$a=Get-Process
foreach($i in $a)
{
    # $_.ProcessName or $_.Name can be used interchangeably
    # $i.ProcessName
    if($i.Name -like "s*")
    {
        Write-Host $i
    }
}

foreach($i in $a)
{
    if($i.Name -notlike "s*")
    {
        Write-Host $i
    }
}